DE1956832C - - Google Patents

Description

An additional measure to stabilize ε-caprolactone is that the with oxygen and / or oxidizing agents and / or acids treated and distilled lactone again with a small Amount (about 0.01 to about 1 percent by weight) of an oxygen donating compound is added. This additional stabilization improves the protection of the lactone, which is already color-stable, especially when if it is at a higher temperature for a long time, e.g. B. to 95 ° C, is heated.

The following examples explain the process according to the invention and its advantages. As a measure the color is the APHA color number of the sample specified. More detailed explanations can be found in H. A. G a r d η e r and G. G. S w a r d, Physical and Chemical Examination, 11th Edition, 1950, H. A. Gardner Laboratory Inc., 4723 E Im St., Bethesda, Maryland, USA.

example 1

100 parts by weight of caprolactone are mixed with 0.5 parts by weight percarbamide and distilled over a period of 1 hour under vacuum at a distillation temperature of 12O ⁰ C without a column, without history separation. A colorless caprolactone distillate is obtained, which remains colorless even after 24 hours of heat treatment in an open vessel in the air at 95 ° C. The APHA color number measurement after this heat treatment gives a value of 0.

Under otherwise identical conditions, 100 parts by weight of caprolactone but without the addition of percarbamide distilled, a colorless caprolactone distillate is also obtained, but not colorless remains; it turns reddish on standing in air at room temperature within 1 to 2 weeks. With heat treatment (24 hours at 95 ° C) the discoloration occurs more quickly. The freshly distilled, initially colorless caprolactone has an APHA color number of 500 after this heat treatment.

Example 2

100 parts by weight of caprolactone are mixed with 1 part by weight of hydrogen peroxide (35% by weight) and the mixture is then ^{distilled off within x} / a hour in vacuo at a distillation ^{temperature of 120 °} C. without a distillation column. The water resulting from the decomposition of hydrogen peroxide is separated off. A colorless caprolactone distillate is obtained which remains colorless even after heat treatment in an open vessel in the air (24 hours at 95 ° C.). The APHA color number measurement after this heat treatment gives a value of 0. This caprolactone remains colorless even after standing for weeks at room temperature, both in an open and in a closed vessel.

A comparative distillation of caprolactone under analogous conditions, but without hydrogen permeation

ao oxide, provides an initially colorless caprolactone distillate, which turns reddish yellow after heat treatment (24 hours at 95 ° C) and an APHA color code of 500 assumes. Even at room temperature, this comparison caprolactone changes color within 1 to

as 2 weeks.

Example 3

Ten experiments are summarized in the table below. Experiment 3 is to be seen as a comparison Blank value. Here the caprolactone was not given an oxygen donor before the distillation or treated with an acid. In experiments 4 to 12, a treatment was carried out before the distillation (0.2 Torr / 80 ° C) to convert impurities that tend to discolour into non-volatile reaction products. Give the indicated APHA color numbers after heat treatment of caprolactone samples an indication of the effectiveness of the treatment agents.

3) 415

Attempt no.

6 17 18 19

10 11

Caprolactone, treated as follows:

without treatment, just distillation
(Comparison)

3 days / 20 ° C air introduced, then

distillation

1 hour / 120 ° C air introduced, then
distillation

1 hour / 120 ° C with 1% H ₂ O ₂ (35%)
treated, then distillation

1 hour / 120 ° C with 0.5% percarbamide
heated, then distillation

1 hour / 120 ° C with 0.1% p-toluenesulfonic acid heated, then distillation

1 hour / 120 ° C with 0.1% concentrated
HCl heated, then distillation

Heated for 1 hour / 120 ° C with 0.5% benzoyl peroxide, then distillation

1 hour / 120 ° C with 0.5 ° / _? Barium peroxide heated, then distillation

1 hour / l 20 ° C heated with 0.5% ammonium persulphate, then distillation

APHA color number after heat treatment:

24 hours / 95 ° C

72 hours / 95 ° C

50

10 10

300

100

50

200

Example 4

If a colorless caprolactone distillate, which was pretreated like Experiment 5 in Example 3 to improve the color (by introducing air for 1 hour / 120 ° C) and which assumes an APHA color number of 50 in the test heat treatment (24 hours / 95 ° C), with 0.1% of its weight of added percarbamide, so (24 hours / 95 ⁰ C) occurs as a result of this further stabilization in an analogous heat treatment only a color change to APHA number 10 a.

At game 5

If a colorless caprolactone distillate is pretreated like Experiment 8 in Example 3 to improve the color was (by heating for 1 hour / 120 ° C with 0.1% p-toluenesulfonic acid) and that in the discoloration test by heat treatment (24 hours / ao 95 ° C) assumes an APHA color number of 300, with 0.1% of its weight is added to percarbamide, so occurs as a result of this further stabilization in a analog heat treatment test (24 hours /

95 ° C only a color change up to APHA color number 75.

Claims (3)

Patent claims: 1. A method for stabilizing ε-caprolactone against discoloration, characterized in that that the lactone with oxygen and / or one or more oxidizing agents and / or one or more acids which are less volatile than the lactone and treated distilled, and optionally the distilled lactone at about 0.01 to about 1 percent by weight, based added to the amount of lactone, one or more oxygen-releasing compounds. 2. The method according to claim 1, characterized in that the treatment of the lactone with about 0.01 to about 3 percent by weight, based on the amount of lactone, of one or more oxidizing agents and / or one or more acids. 3. The method according to claim 1, characterized in that at a temperature between about 0 and about 250 ° C and at a pressure between 0.1 Torr and normal pressure works.